Shower "pulsing" when turned on.

bowers 1 Posts 1 Karma
bowers posted this 29 September 2015

As a result of poor water pressure a Plumber reccommended fitting a pump, which he did..fitting a Shower mate Eco Standard Twin  46502 (15mm).

while the water pressure did improve it still doesnt appear great but may be due to the newly fitted shower head being 8inch Rain shower head.

The main concern is that the water is now "pulsing" as the pump kicks in and out every 10 seconds or so.  I cant see where any blockage could be.

I noticed that the pump was fitted (beside Hot water Cylinder)  with a 22mm  supply( Hot and Cold)  reduced to 15mm flex connector into the pump and 15mm flex connectors back out of the pump increased to 22mm (hot and cold) to the shower  unit (4 metres away)    where it reduces to 15MM again to connect to the mixer valve.

Is this O.K and couldit cause the "pulsing" ?


PumpAssist 261 Posts 192 Karma
PumpAssist posted this 29 September 2015

We hear this problem quite a lot with eco pumps fitted to rain head showers.

Usually the shower works ok on fully hot or fully cold but pulses when mixed. If this is the case, the water isn't escaping quickly enough from the shower head which then creates too much back pressure and effectively the floats in the pump are pushed back down and the water movement at the pump stops which turns the pump off. The pressure then decreases when the water gets away and so the pump starts again. Usually this is the result of either a scaled up shower head, a blockage in the hose (if fitted) or a blockage in the shower valve.

Sometimes the pulsing occurs regardless of the temperature setting on the shower. If this is the case I would try and get some figures for the shower. Ideally the minimum operating pressure of the shower valve and the flow rate of the shower head. If the shower head is quite a high flow rate (15 lpm for example) then that pump will be producing  0.8 bar pressure (without taking into account the losses in the system). It may be that that pressure is too low for the shower to operate correctly and a larger pump may be needed.

Francis 1 Posts 1 Karma
Francis posted this 25 January 2018

1.       We bought house 18 months ago with an en-suite with a Bristan Sonique shower control (thermostatically controlled mixer). The shower was fed by a New Team Duraspeed Shower Pump (1.5bar) and about 7 metres of up and over ½ inch pipe. The pump is fed by gravity from a roof tank about 1.5 metres above the shower head. On 21/1/2018 the pump started to leak through its casing. Before that it worked fine, if somewhat noisily.

2.       We called a plumber and he advised replacing the pump with a Stuart Turner. I bought a Stuart Turner Showermate Eco S Positive Head Twin Shower Pump 1.5bar and he installed it.

3.       Unfortunately things are not working properly. The pump pulses off and on.

4.       The plumber spent over 2 hours trying to resolve this.

a.       Hot and cold both get through to the shower by gravity when the pump is turned off.

b.      There is an access panel behind the shower with isolation valves for the shower. He closed the valves, disconnected the pipework below the valves and then tested the flow with the pump on to that point. No problem.

c.       He removed the shower hose and head. Turning on the shower still caused the pump to pulse.

d.      The problem would appear to be the resistance to the flow from the thermostatic shower control. The valve still works fine with just a gravity feed. Stripping the valve and soaking it in descaler has not  helped.

What have I done wrong? What do I do now?

PumpAssist 261 Posts 192 Karma
PumpAssist posted this 25 January 2018

The shower valve is causing the problem. It may have flow restrictors fitted and you are then getting the issue in the post above. Here is a link to the installation manual for the Sonique 2 valve, where you will be able to see the filters and flow restrictors. Its worth checking the filters are clean as they can cause the same issue if blocked.